The present invention is directed to a device for multiplying the quantity of cellular mobile phone identification call numbers or telephone numbers for one mobile phone unit. Cellular mobile phones are typically mounted in an automobile, truck, van or the like, allowing access to fixed-wire telephone systems, as well as other mobile phones, whereby a mobile phone user may call a fixed land-based phone or another mobile phone.
Under present conditions, the cellular mobile phone system is divided into a plurality of cells or grids defined by stationary transmitter-receiver stations, each of which is connected to a switching station connecting the cell or grid to the land-based, fixed-wire telephone system. Each cell or grid is designed to allow each mobile phone access to the land-based phone system, or to allow a land-based or mobile phone access to another mobile phone, according to a principle in which that cell that receives the transmitting and/or receiving signal from a mobile phone or mobile phones is that cell which is made operative for transmitting and/or receiving the call. Thus, for example, when a mobile phone subscriber attempts to make a phone call to another mobile phone, or a land-based phone, that cell which receives the strongest signal from the transmitter of that particular mobile phone is the one made operative for connection to the phone being called. If, after connection or during the initialization of the call, the calling mobile phone travels beyond the effective range of the cell originally handling the call, another cell which receives the signal stronger than the original cell, receives the transmitting signal from the calling mobile phone, and an automatic system transfer from the first cell to the second cell occurs. Thus, during the process of calling, and during the call itself, whenever the mobile phone transfers from the effective range of a first cell to the effective range of a second cell, the second cell takes over from the first cell. This may occur many times, depending upon the distance the mobile phone unit travels during the telephone call, and depending upon the number of effective cell zones through which the phone may travel.
Each mobile unit, which is comprised of a transmitter-receiver (commonly referred to as a transceiver), includes a call-channel selector which controls a frequency synthesizer to span the available call-channel frequencies and, in combination with a microprocessor, selects that call-channel which is received the strongest in order to select the cell closest to the mobile unit. Each mobile phone has its own unique telephone or user number by which it may be accessed by another mobile phone or land-based mobile phone. With presently known and used systems, each moble phone is allowed only one such telephone number. This unique number is included on a ROM chip addressed by the microprocessor of the mobile unit. However, because only one user number is possible for each mobile unit, the owner of such mobile unit is restricted to only one mobile telephone service.
Since each mobile phone unit can presently include only one telephone number, this limits the range of use of the mobile unit, and prevents the possibility of using more than one cellular phone company, thus, taking advantage of different time rates and access rates. If a mobile unit could have a pair of telephone numbers, one telephone number for a first telephone company, and a second telephone number for a second telephone company, it is possible to use each phone company at those times when their rates are the lowest, in order to save money. For example, if the first telephone company offers lower rates at night, while the second telephone company offers lower rates during the day, a mobile unit having two telephone numbers could use the first telephone company's system at night, and use the second telephone company's system during the day, at considerable savings.
Further savings are achieved when a mobile unit extends beyond its home area. Typically, when a mobile unit goes beyond the defined radius of its home base (defined by the telephone company), they are charged an additional fee, called the "transit fee," for accessing a telephone company in the new region, regardless of whether it is the usersubscribed telephone company. Thus, if one were able to have two telephone numbers for the same mobile unit, the first telephone number could be used for the home-based telephone system, while the second telephone number could be used for another telephone system, or another system outside the same home-based area, when the mobile unit extends beyond the home region. Under present conditions, when a user wishes to transfer from his subscribed system to a competitor's system to achieve a better connection or complete a call outside his home area, roaming fees are also charged the customer when he uses another company's system. This roaming is usually achieved by an "A/B" switch, which switches over from even channel frequencies of the home company to the odd channel frequencies of the other company. In many cities and regions, however, it is not possible to access a second telephone company. Therefore, in addition to providing potential economical savings by having more than one telephone number for each mobile unit, it is also possible to make calls which, in certain situations, have been impossible. Further, if more than one telephone number could be used for each mobile unit, and each mobile unit could subscribe to more than one telephone company, in the event a telephone call made on one system was a poor connection, the user may readily transfer to the other system where, more often than not, the call would be a clearer connection. Also, by having more than one telephone number, each mobile unit could have one telephone number for outgoing calls only, and have the second telephone number for incoming calls only. This could be beneficial in limousines, emergency vehicles (such as ambulances), security vehicles, and the like. Further, by having more than one telephone number, one may have a separate telephone number for a frequently visited area, such as for a salesman's territory or a truck driver's route, where the user would have one telephone number for use in the area frequently visited. In this case, the user could avoid long distance costs, as well as roaming charges and transit fees.